Comprised of 450 instrumental records from temperature stations sheltered from ocean-air/urbanization/adjustment biases throughout the world, a new 20th/21st century global temperature record introduced previously here very closely aligns with paleoclimate evidence from tree rings, ice cores, fossil pollen and other temperature proxies.

The Alignment Of Paleoclimate Proxy Data & Instrumental Records

The paleoclimate proxy data for the Northern Hemisphere (NH) consistently show an oscillation rather than a linear warming trend between 1900 and 2010: (a) a substantial warming trend between 1900 and the early 1940s, (b) a substantial cooling trend between the 1940s and 1970s, and (c) a subsequent warming trend since the 1980s that matches or comes close to matching the warming peaks in the 1930s and early 1940s (rather than greatly exceeding it).

A New Instrumental Record Of The Northern Hemisphere

In a ground-breaking new paper (Lansner and Pepke Pedersen, 2018) published in the journal Energy and Environment, an analysis of land surface instrumental records from across the globe’s ocean air sheltered (OAS) regions reveals that, like the proxy evidence presented above, most of the modern era warming occurred prior to the 1940s, and the there has effectively been no net warming since then.

Lansner and Pepke Pedersen (2018) point out that, due to the divergent rates of warming and cooling for land vs. ocean water, there is a significant difference in the range of temperature for the regions of the world influenced by their close proximity to oceans and coastal wind currents (ocean air affected, or OAA) and the inland regions of the world that are unaffected by ocean air effects and coastal wind because they are sheltered by hills and mountains or located in valleys (ocean air sheltered, or OAS).

The two authors acknowledge that it is “difficult” to isolate the influence of the ocean’s effects on temperature changes and the influence of climate- or radiation-induced changes in driving temperature change. So the two authors chose to “retrieve temperature data where impact of the ocean temperature trends has been reduced as much as possible.”

The results they obtained in analyzing “thousands” of instrumental temperatures from across the globe are especially noteworthy. To summarize, Lansner and Pepke Pedersen (2018) found that the OAS regions of the world reached annual temperatures that were just as warm or warmer during the 1920s to 1940s as they have been in recent decades. There has been no net warming — and, in fact, an overall slight cooling — since the 1940s for the OAS temperature stations.

“We found that in any land area with variation in the topography, for the period 1900-2010 we can divide the meteorological stations into the more warm-trended ocean air-affected OAA-stations, and the more cold-trended ocean air-sheltered OAS-stations. The methods used in this work are meant to give a rough picture of the large differences in temperature trends between OAS and OAA stations. … When we isolated temperature trends 1900–2010 with as little ocean influence as possible – the OAS areas – we found a warm period 1920–1950 with temperatures similar to recent decades for all investigated areas worldwide. We have not found any area with numerous OAS/Valley stations available where the majority of temperature stations show a different result.”

“In contrast, the OAA locations like islands, coasts, hills facing dominating ocean winds, etc., did not reflect the warm period 1920–1950 well. … Therefore, the lack of warming in the OAS temperature trends after 1950 should be considered when evaluating the climatic effects of changes in the Earth’s atmospheric trace amounts of greenhouse gasses as well as variations in solar conditions.”

“In locations best sheltered and protected against ocean air influence, the vast majority of thermometers worldwide trends show temperatures in recent decades rather similar to the 1920–1950 period. This indicates that the present-day atmosphere and heat balance over the Earth cannot warm areas – typically valleys – worldwide in good shelter from ocean trends notably more than the atmosphere could in the 1920–1950 period.”

1.“[W]e show in Figure 3 the results for the Scandinavian area where we have used a total of 49 OAS stations and 18 OAA stations. The large number of stations available is due to the use of meteorological yearbooks as supplement to data sources such as ECA&D climate data and Nordklim database. … For the years 1920–1950, we thus find temperatures in the OAS area to be up to 1 K warmer than temperature in the OAA area.”

2. “Another example is from Central Siberia (Figure 4), where a total of 18 OAS stations and 17 OAA stations were used. All data were taken from GHCN v2, raw data. … Again we find that the temperature trends from the OAS area show more warming in the 1920-1950 period with about 0.5–1.5 K higher temperatures than the OAA areas.”

3. “In the Central Balkan area [Poland, Slovakia, Austria, Hungary, Slovenia, Croatia, Serbia, Rumania, Greece, and Turkey] (Figure 5), 41 OAS stations and 25 OAA stations were used … data from meteorological yearbooks and statistical yearbooks supplemented with GHCN v2 raw (NOAA) and BEST raw data. … The temperature trends from the OAS area from the 1925 to 1950 period are found in most years to be around 1 K warmer than temperature trends from the OAA areas.”

4. “For the USA (Figure 6), we defined the OAS area as consisting of eight boxes, each of size 5° X 5°. … A total of 236 temperature stations were used from this area. … All data were taken from GHCN v2 raw data. … Again the temperature trends from the OAS area as defined above show the 1920–1955 period in most years to be around 1 K warmer than temperature trends from the OAA areas.”

5. “For Central China (Figure 7), 14 OAS stations and 12 OAA stations were used. All data were taken from GHCN v2 raw data. …The temperature trends from the OAS area show the 1920–1950 period around 0.5–1.5 K warmer than temperature trends from the OAA areas.”

6. “For the Pakistan/NW India area (Figure 8), 10 OAS stations and 8 OAA stations were used. All data were taken from GHCN v2 raw data. … The temperature trends from the OAS area show the 1930–1955 period to be around 1–1.5 K warmer than temperature trends from the OAA areas.”

7. “In the Sahel area (Figure 9), 34 OAS stations and 11 OAA stations were used. All data were taken from GHCN v2 raw data. The temperature trends from the OAS area show the 1930–1950 period to be around 0.2–1 K warmer than temperature trends from the OAA areas.”

8. “For Southern Africa (Figure 10), 13 OAS stations and 15 OAA stations were used. All data were taken from GHCN v2 raw data. The temperature trends from the OAS area as defined show the 1920–1945 period to be around 0.2–1.5 K warmer than temperature trends from the OAA areas.”

9. “For South East Australia (Figure 11), 18 OAS stations and 24 OAA stations were used and all data were taken from GHCN v2 raw data. … The temperature trends from the OAS areas show the 1925–1950 period to be around 0.3–0.5 K warmer than temperature trends from the OAA areas.”

10. “Finally, for Central South America (Figure 12), 17 OAS stations and 13 OAA stations were used. Data were taken from GHCN v2 raw data and also from the BEST raw data base. … The temperature trends from the OAS area as defined show the 1930–1965 period to be around 0.5–1 K warmer than temperature trends from the OAA areas.”

Global Temperatures In Non-Urban Areas Have Warmed By 0.375 K/Century Since 1900

Combining the OAS temperatures and OAA temperatures and using the century-scale trends for each identified in the paper (-0.03 K/century and +0.78 K/century, respectively), it may be concluded that instrumental temperature stations located in non-urban areas and not subjected to artificial urban heating bias produce an overall warming trend of just 0.375 K/century (0.038 K/decade) during 1900-2010.

“For the OAS areas, we find a linear temperature trend over the whole period from, 1900 to, 2010 of -0.03 K/century whereas we find 0.78 K/century for the OAA areas. We recognize the remarkable temperature increase in temperature in the years after the 1918/1919 strong El Nino. After this warming, the OAS temperature data appear to have jumped by around 0.5 K to a new level, indicative of a shift to a new climatic regime. The OAA data fail to show this abrupt change.”

This much milder rate of warming over the 20th/21st centuries underscores just how influential urbanization might have been in driving up warming artificially, or non-climatically, during the modern era.

The phenomenon of artificially-driven warming rates has been documented in many other analyses.

“We should also consider the role of the Bureau of Meteorology. The climate trend maps compiled by Bureau of Meteorology in their climate change section are completely unreliable, as the alleged increasing temperature is obtained by lowering temperatures of the past by “adjustments“.

“The global reconstructions as GISS (Hansen et al. 2010, GISTEMP Team 2017) are artificially biased upwards to reproduce the carbon dioxide emission trend, but the strong natural oscillation signal prevails. The very likely overrated warming rate since 1880 is 0.00654°C/year or 0.654°C/century. This rate increases to 0.00851°C/year or 0.851°C/century by considering the data only since 1910. The warming rate cleared of the oscillations is about constant since the 1940s.”

“There are stations covering different time windows having very close patterns of temperatures. In this circle of 3,141,593 km2 (roughly 50% of Australia) that is mostly underdeveloped, none of the stations […] actually has a warming trend. … It is therefore only an artefact by BOM to produce the warming. Homogenization is supposed to be used to account for upwards biases such as Urban Heat Island, not to introduce upwards biases. … The longest of the Australian temperature records that were considered the most reliable by Bureau of Meteorology on February 2009 (BOM 2009) are still available as raw temperatures in the climate data online section and consistently show no warming and no increased extreme events within the limit of accuracy of measurements.”

“New Zealand’s national record for the period 1909 to 2009 is analysed and the data homogenized. Current New Zealand century-long climatology based on 1981 methods produces a trend of 0.91 °C per century. Our analysis, which uses updated measurement techniques and corrects for shelter-contaminated data, produces a trend of 0.28 °C per century.”

“The long-term mean annual temperature record (1885 –1993) shows warming over the past century, with much of the warming occurring in the most recent three decades. However, our analyses show that half or more of this recent warming may be related to urban growth, and not to any widespread regional temperature increase.”

“We examine the urban effect on surface warming in Eastern China, where a substantial portion of the land area has undergone rapid urbanization in the last few decades. Daily surface air temperature records during the period 1971–2010 at 277 meteorological stations are used to investigate temperature changes. Owing to urban expansion, some of the stations formerly located in rural areas are becoming increasingly influenced by urban environments. To estimate the effect of this urbanization on observed surface warming, the stations are dynamically classified into urban and rural types based on the land use data for four periods, i.e. 1980, 1990, 2000 and 2010. After eliminating the temperature trend bias induced by time-varying latitudinal distributions of urban and rural stations, the estimated urban-induced trends in the daily minimum and mean temperature are 0.167 and 0.085 °C decade−1, accounting for 33.6 and 22.4% of total surface warming, respectively. The temperature difference between urban and rural stations indicates that urban heat island intensity has dramatically increased owing to rapid urbanization, and is highly correlated with the difference in fractional coverage of artificial surfaces between these two types of stations. This study highlights the importance of dynamic station classification in estimating the contribution of urbanization to long-term surface warming over large areas.“

Artificial Amplification of Warming Trends …Western United States “Observations from the main mountain climate station network in the western United States (US) suggest that higher elevations are warming faster than lower elevations. This has led to the assumption that elevation-dependent warming is prevalent throughout the region with impacts to water resources and ecosystem services. Here, we critically evaluate this network’s temperature observations and show that extreme warming observed at higher elevations is the result of systematic artifacts and not climatic conditions. With artifacts removed, the network’s 1991–2012 minimum temperature trend decreases from +1.16 °C decade−1 to +0.106 °C decade−1 and is statistically indistinguishable from lower elevation trends. Moreover, longer-term widely used gridded climate products propagate the spurious temperature trend, thereby amplifying 1981–2012 western US elevation-dependent warming by +217 to +562%. In the context of a warming climate, this artificial amplification of mountain climate trends has likely compromised our ability to accurately attribute climate change impacts across the mountainous western US.”

“The annual urban warming at the city stations can account for about 65∼80% of the overall warming in 1961∼2000, and about 40∼61% of the overall warming in 1981∼2000.”

“UHI [the Urban Heat Island effect] accounts for almost half of Athens’ warming. … The study explores the interdecadal and seasonal variability of the urban heat island (UHI) intensity in the city of Athens. Daily air temperature data from a set of urban and surrounding non urban stations over the period 1970–2004 were used. Nighttime and daytime heat island revealed different characteristics as regards the mean amplitude, seasonal variability and temporal variation and trends. The difference of the annual mean air temperature between urban and rural stations exhibited a progressive statistically significant increase over the studied period, with rates equal to +0.2 °C/decade.”

“[E]xtraneous (nonclimatic) signals contaminate gridded climate data. The patterns of contamination are detectable in both rich and poor countries and are relatively stronger in countries where real income is growing. We apply a battery of model specification tests to rule out spurious correlations and endogeneity bias. We conclude that the data contamination likely leads to an overstatement of actual trends over land. Using the regression model to filter the extraneous, nonclimatic effects reduces the estimated 1980–2002 global average temperature trend over land by about half.“